1. Technical Field
The invention relates to a gyro sensor, an electronic apparatus, and a method of manufacturing a gyro sensor.
2. Related Art
In recent years, inertial sensors that detect a physical quantity using a silicon microelectromechanical system (MEMS) technique have been developed. Among these inertial sensors, a gyro sensor (angular velocity sensor) that detects angular velocity is used for a hand-shake correction function of digital still cameras (DSC), a motion sensing technique of game machines, and the like.
The gyro sensor includes a driving portion that is actively vibrated and a detecting portion that is displaced by a Coriolis force when an angular velocity is applied. Thus, it is possible to detect an angular velocity from the displacement amount of the detecting portion. In such a gyro sensor, since a difference (detuning frequency) between the resonant frequency of the driving portion and the resonant frequency of the detecting portion in particular has a direct influence on the sensitivity and detection band of the gyro sensor, frequency control is very important. As a method of adjusting frequencies, for example, JP-A-11-83498 discloses an adjustment method that uses laser light.
However, in the case of the adjustment method that uses laser light, there is a limit on a range of frequencies that can be adjusted by a laser apparatus. Thus, it may be difficult to adjust the frequencies if a frequency fluctuation is greater than the limit. Moreover, when any one of the resonant frequency of the driving portion and the resonant frequency of the detecting portion is adjusted, the other resonant frequency may also be changed. As a result, it is difficult to obtain a desired detuning frequency, and the sensitivity properties and the detection band properties of the gyro sensor may deteriorate.
Moreover, when a structural body is vibrated using electrostatic force, there is known a method of adjusting the resonant frequency using a damping effect of a spring due to the Coulomb force. However, if the electrostatic force is increased too much, a sticking phenomenon of the structural body may occur. Thus, a resonant frequency adjustment method that uses electrostatic force may cause the risk of sticking, and there is a problem in that it is difficult to adjust the frequency dramatically.